A high-resolution ammonia emission inventory in China

The existence of gas-phase ammonia (NH3) in the atmosphere and its interaction with other trace chemical species could have a substantial impact on tropospheric chemistry and global climate change. China is a large agricultural country with an enormous animal population, tremendous nitrogen fertilizer consumption and, consequently, a large emission of NH3. Despite the importance of NH3 in the global nitrogen (N) cycle, considerable inaccuracies and uncertainty exist regarding its emission in China. In this study, a comprehensive NH3 emission inventory was compiled for China on a 1 km x 1 km grid, which is suitable for input to atmospheric models. We attempted to estimate NH3 emissions accurately by taking into consideration as many native experiment results as possible and parameterizing the emission factors (EFs) by the ambient temperature, soil acidity and other factors. The total NH3 emission in China was approximately 9.8 Tg in 2006. The emission sources considered included livestock excreta (5.3 Tg), fertilizer application (3.2 Tg), agricultural soil (0.2 Tg), nitrogen-fixing plants (0.05 Tg), crop residue compost (0.3 Tg), biomass burning (0.1 Tg), urine from rural populations (0.2 Tg), chemical industry (0.2 Tg), waste disposal (0.1 Tg) and traffic (0.1 Tg). The regions with the highest emission rates are located in Central and Southwest China. Seasonally, the peak ammonia emissions occur in spring and summer.